Fundamentals of Electrodics Fall semester, 2011 Shu-Yong Zhang

Electrode process The totality of changes occurring at or near an electrode during the passage of current. electrochemical step: involving gain or loss of electron non-electrochemical step Electrochemical thermodynamics Electrochemical kinetics

1.1.1 Electrochemical apparatus: galvanic cell Electrolytic cell Electrodes: positive/negative electrode anode / cathode §1.1 Review of fundamental electrochemistry

1.1.2 Types of electrode: 1) metal / metal ion electrode 2) metal / insoluble salt electrode 3) redox electrode 4) membrane electrode 5) intercalation electrode 6) modification electrode 7) semiconductor electrode 8) insulator electrode

Conversion film formation Kind of electrode reactionDirect Reaction of electrode 1) Active Dissolution 2) Surface finishing 3) Passivation 4) Surface conversion 5) Anodization Reaction of species from solution 1) Oxidation / Reduction 2) Polymerization 3) deposition Indirect via electron media Reaction of species in solution 1) Oxidation via Ce 4+ 2) Reduction via V 2+ 3) Polymerization 4) deposition Direct and indirect electrochemical reactions

working electrode (W. E.) counter electrode (auxiliary electrode) (C. E.) reference electrode (R. E.) 1) Three-electrode system/cell: Measurement of electrode polarization Luggin cappilary

Shape of working electrode disk sphere wire ring band foil array Interdigitaled array

Commercial SCE 2) Typical reference electrode: Commercial Ag/AgCl or Ag/Ag + electrode

1 ） Faraday’s Law m, mass of liberated matter; Q electric coulomb, z electrochemical equivalence, F Faraday’s constant, M molar weight of the matter.> F =    = C mol -1  C mol -1 §1.1.5 Important relationships

Valid only for reversible cell 2 ） Nernst equation: Dependent of electrode potential on species activities

3) Tafel equation: The point of intersection of the extrapolation on the line  = 0 is log i 0. A is in fact the  at j = 1 A cm -2.  = a + b log j Valid only for irreversible cell

Pt electrode in aq M Fe 3+, Sn 4+, Ni 2+ (1 M HCl) Discharge series: As potential moved to more negative values, the substance which will be reduced first is the oxidant with the least negative . §1.2 Physical meanings of  and I 1) Electrode potential

the highest occupied level Electron gas Metal atoms unoccupied Fermi Level occupied Energy bands Fermi-Dirac distribution cf. p

Electrode Solution A + e -  A - Electrode Solution Occupied MO Vacant MO Electrode Solution Occupied MO Vacant MO Electrode Solution A  A + + e -

HOMO approximately corresponds to   of A/A - LUMO approximately corresponds to   of A + /A physical meaning of  ? The tendency to accept or donate electrons is represented by the sign and absolute value of the standard electrode potentials. That means: high positive potential values indicate a strong tendency for accepting electrons A higher positive potential of a given half-cell with respect to another indicates that the former has stronger oxidizing ability than the latter. That means: high positive potential values indicate a strong tendency for accepting electrons A higher positive potential of a given half-cell with respect to another indicates that the former has stronger oxidizing ability than the latter.

Current: the index of reaction rate Consider 1 mole of A - is oxidized to A A   A + ne  Q = n N F n: the number of e - transferred, N the number of mole of A 2) Electrochemical current

§1.3 Electrochemical methods One cannot simultaneously control both E and I Control E: potentiostatic methods Control I: galvanostatic methods Voltammetry Voltammetric method

References: [1] 查全性等，《电极过程动力学导论（第三版）》，科 学出版社，北京， [2] A. J. Bard, Electrochemical Methods–Fundamentals and Applications (2 nd, Ed.), John Wiley & Sons. [3] Encyclopedia of Electrochemistry, (Ed. A.J. Bard), Wiley. [4] Modern Electrochemistry, (Ed. J. O. Bockris ), Springer. [5] Modern Aspects of Electrochemistry, Springer. [6] A. H. Frumkin, Kinetics of Electrode Process, Science Press.

Allen J. Bard, Martin Stratmann, Encyclopedia of Electrochemistry, Wiley. Vol. 1: Thermodynamics and Electrified Interfaces Vol. 2: Interfacial Kinetics and Mass Transport Vol. 3: Instrumentation and Electroanalytical Chemistry Vol. 4: Corrosion and Oxide Films Vol. 5: Electrochemical Engineering Vol. 6: Semiconductor Electrodes and Photoelectrochemistry Vol. 7: Inorganic Electrochemistry Vol. 8: Organic Electrochemistry Vol. 9: Bioelectrochemistry Vol. 10: Modified Electrodes Vol. 11: Index

Modern Aspects Of Electrochemistry, Vol. 42 Topics include: 1) The electrochemistry and electrocatalysis of Ruthenium in regards to the development of electrodes for Polymer Electrolyte Membrane fuel cells (PEM) 2) Breakthroughs in Solid Oxide Fuel Cell (SOFC) anodes and cathodes leading to improved electrocatalysis 3) Electrocatalysis of the electrochemical reduction of CO 2 on numerous metals 4) The interfacial phenomena of electrodeposition and codeposition, and the need for new theoretical analyses of the electrode-electrolyte interface 5) Advantages of scanning tunneling microscopy (STM) in understanding the basics of catalysis, electrocatalysis and electrodeposition 6) The role of electrochemistry in emerging technologies including electrodeposition and electroforming at the micro and nano levels, semiconductor and information storage, including magnetic storage devices, and modern medicine

Bockris, John O'M., Reddy, Amulya K.N., Modern Electrochemistry, Springer. Vol. 1 Ionics Vol. 2A Fundamentals of Electrodics Vol. 2B Electrodics in Chemistry, Engineering, Biology and Environmental Science